How it works
Ovulation usually occurs about two weeks before the next period. The fertile window starts a few days before and ends shortly after ovulation.
Ovulation calculator · Marrakech
Ovulation and fertile window calculator
Enter the first day of your last period and your usual cycle length: the tool estimates your likely ovulation day, your most fertile window and your next period. It is an estimate, most useful if your cycles are regular.
A fertile window, not a single day
The egg survives only about 12 to 24 hours, but sperm can survive up to 5 days in the genital tract. The fertile window therefore covers the 5 days before ovulation and the day of ovulation. The two or three days before ovulation are the most favourable: the tool highlights them.
Adjustable luteal phase
Ovulation occurs on average 14 days before the next period. This length, called the luteal phase, varies from 10 to 16 days between women. You can change it if you know it (for example from a temperature chart): the estimated ovulation moves accordingly.
Irregular cycles: a wider window
If your cycles vary, a precise day cannot be predicted. The tool then calculates a wider window from your shortest and longest cycles. If your cycles are very irregular or absent, consult: a cause is almost always found (see the Gynaecological endocrinology page).
To refine: tests and signs
An ovulation test (LH hormone in urine) announces the coming ovulation. A temperature chart only confirms it afterwards. Clear, stretchy mucus is a sign that ovulation is near. No method is perfect: this calculation is an aid, not a certainty.
It is not contraception
This calculator must not be used to avoid pregnancy: ovulation can occur earlier or later than predicted. For reliable contraception, consult.
Limits
The calculation is less reliable if your cycles are irregular. This tool is not a method of contraception.
Frequently asked questions
Can this tool be used as contraception?
No. It gives an estimate and does not protect against pregnancy.
My cycles are irregular, what should I do?
Discuss it at a consultation: cycle monitoring or an assessment can be offered.
Is my data saved?
No, dates stay on your device and nothing is sent.
When should we have intercourse to conceive?
In the fertile window, ideally every one to two days, especially the two or three days before ovulation.
How long before consulting?
After 12 months of trying without pregnancy, or 6 months after 35, or sooner if cycles are very irregular.
My cycle is 35 days: is the calculation valid?
Yes, ovulation is estimated from your cycle length and luteal phase. It will occur later than day 14.
Also of interest
Informational content: it does not replace a consultation. No outcome can be guaranteed.